Chapter 18: MMDS and LMDS

Multichannel Multipoint Distribution Service (MMDS)

    MMDS (Multichannel Multipoint Distribution Service) is a Multichannel broadcast service that operates in the 2.0 to 2.9 GHz. Frequency range. It’s designed to be a point to multipoint broadcast service that is capable of delivering multiple channels of television programming for digital or analogue mode together with internet access, telephone and data transfer services to individual receive sites. Channels containing video, audio and data transmitter from a central site to individual residences, multiple dwelling units, and business locations. MMDS systems, which can be configured to offer just television, are commonly referred to as “Wireless Cable Television”.

Specifications of MMDS

Fixed/Mobile	Fixed
Circuit/Packet	n/a
Max Bandwidth	10Mb
Range	70 miles
Frequency	2.5GHz-2.686Ghz
Host Network	None
Definer	IEEE (Institute of Electrical and Electronic Engineers)

How does MMDS System work?

     The architecture of a typical wireless cable system can be divided into two basic nodes: transmitting sites and receiving sites. Transmitting sites are the main or “HUB” node of MMDS system.

     Programming information is generally delivered to an MMDS system from satellites, it can also be generated locally or come from pre-recorded video tapes, these signals are fed into discrete transmitters where they are modulated up converted and amplified. Transmitter powers range 1 to 200 watts per channel and 15 to 100 watts average power per digital channel, individual microwave channels are then multiplexed or combined together and are passed to a transmitting antenna via low loss coaxial cable or waveguide. A centrally located transmitting antenna radiates the MMDS signal to the desired receiving sites, generally in an omni directional (360 degrees) pattern.

Advantages of MMDS

     Construction of the MMDS transmit site can generally be accomplished in a few weeks to a few months whereas a conventional cable TV system may require in excess of three years. A conventional cable TV system requires a dedicated coaxial “wire” to be connected to each subscriber.

      Another advantage of an MMDS system is the picture quality. A properly designed MMDS system will deliver clear, distortion free pictures to each subscriber’s home. Since the signals do not have to pass through many kilometers of coaxial cable and numerous amplifier chains, the noise associated with typical cable systems is not introduced to MMDS signals. The overall result is better picture quality and greater subscriber satisfaction.

     The third advantage of an MMDS system is the reduced capital expenditure. The majority of the capital invested in an MMDS system is goes directly into the subscriber’s receive equipment. A minimal capital investment is required to install a transmit station. Therefore, as soon as a subscriber is installed, revenue is immediately generated.

    The fourth advantage of an MMDS system is greater reliability. Since conventional cable signals are delivered through many chains of line amplifiers, there is a greater chance for service interruptions (amplifiers are pole and strand mounted). MMDS electronic equipment is generally co-located, yielding much easier system maintenance. MMDS transmit sites are located in climate controlled equipment shelters for maximum performance and greater system reliability.

Local Multipoint Distribution Service (LMDS)

    It is a type of high-speed wireless internet transmission which works using microwaves. At one time, it was seen as a potential solution for expanding home broadband services, particularly in the united States. Today it appears somewhat outdated and has generally been over taken by rival technologies.

    The microwave used by the LMDS system are of a much higher frequency than radio waves. whereas most current wireless internet services broadcast on frequencies of around 2 to 3GHz, LMDS uses frequencies around 26 to 31GHz. The exact frequencies used vary from location to location and ranges may be limited by local regulation and licensing.

    The main uses of LMDS is a point-to-multipoint communication system. This Means that information can be transferred from one point, the local Station, to multiple users. Information transmitted back by any one user only goes back to the local station, rather than to all other users.

LMDS Specifications

Fixed/Mobile	Fixed
Circuit/Packet:	n/a
Max Bandwidth	1.5Gb downstream, 200Mb upstream
Range	4 miles
Frequency	27.5GHz-28.35Ghz, 29.1Ghz-29.25Ghz, 31.075Ghz-31.225Ghz, 31.Ghz-31.075Ghz, 31.225Ghz-31.3Ghz
Host Network	None
Definer	IEEE (Institute of Electrical and Electronic Engineers)

Advantages of LMDS Technology

    The biggest advantage of LMDS technology is derive from the wireless nature: it gave operators an opportunity to provide consumers with access bandwidth and two-way capability without digging up streets. This one fact that no right-of-way clearances are required to deploy it makes it sufficiently inclining as a technology. LMDS has huge chunks of under-utilized spectrum ready to go, more than to satisfy pent-up demand for voice, private data networks, and high speed internet access.

    In addition, this advantage has provided today cellular operators across the globe an economical way to quickly deploy cell sites to provide next generation of bandwidth intensive data services, beyond the traditional voice service.

Why LMDS?

    Point-to-point fixed wireless networks have been commonly deployed to offer high-speed dedicated links between high-density nodes in a network. More recent advances in a point-to-multipoint technology is that it offer service providers a method of providing high-capacity local access that is less capital-intensive than a wireline solution, faster to deploy than a wireline, and able to offer a combination of applications. Moreover, as a large part of a wireless network's cost is not incurred until the costumer premises equipment(CPE) is installed, the network services operator can time capital expenditures to coincide with the signing of new costumers. LMDS provides an effective last-mile solution for the incumbent service provider and can be used by competitive service providers to deliver services directly to end users. Benefit can be summarize as follows:

• Lower entry and deployment cost
• Ease and speed of deployment(system can be deployed rapidly with minimal disruption to the community and the environment).
• Fast realization of revenue(as a result of rapid deployment).
• Demand-based build-out.
• Cost shift from fixed to variable components.
• No stranded capital when costumers churn
• cost-effective network maintenance, management, and operating costs.

    Via the transmission of microwave signals, LMDS networks can provide two-way broadband services including video, high-speed internet access, and telephony services. LMDS leap frogs all the hurdles encountered when wired networks must be deployed. It  really could be the answer to the long sought solution to last mile broadband in the world. Breakthroughs in radio technology, along with increased industry confidence following the success of personal communication service(PCS) and cellular mobile service, have dramatically improved confidence in radio as a reliable local access technology. LMDS, as a technology is mature and reliable and delivers compelling advantages for adoption in the world.